To take advantage of special postal pre-sort rates for mass mailings, mail must be sorted and banded in stacks of at least 10 pieces, with each envelope in each stack being addressed to an address in the same ZIP code. Prior art computer-controlled, automated mailing systems have been developed which have the capacity of printing and separating mail at relatively high speeds, for example, 6,000 pieces per hour. Computer generated statements and invoices for large public utilities or department stores often are mailed using such automated mailing systems.
Typically automated high-speed mailing systems will print a statement or document at a computer printer on computer form paper. The individual statements are separated at a burster, which also may fold the statements. Thereafter, a collator/inserter will add additional documents, such as advertisements and return envelopes, and insert the assembled statement and documents into an envelope. The envelope will be sealed and postage applied at a postage meter mailing machine. The mail exits from the postage meter mailing machine with envelopes being fed serially into a stacker. The stacked envelopes are conveyed to an automated banding apparatus or manual banding stations for the application of one or two rubber bands around the mail stack. Once banded, the mail can be delivered to a postal facility and will be entitled to bulk mailing postal rates.
The ability of take advantage of the lower bulk mailing postal rates is quite significant. A standard one ounce letter currently has a regular postal rate of twenty-five cents. If mail is stacked in bundles having at least ten pieces, but not having a height exceeding three and one-half inches, and if all of the pieces of the mail in the stack have the same ZIP code, a bulk rate of twenty-one cents per one ounce piece of mail can be used. If the mail is further pre-sorted into stacks separated by carrier route, that is, the same ZIP code and the same four additional carrier route numbers, the mail will be entitled to a rate of eighteen cents per one ounce piece.
Known prior art automated apparatus and processes for assembling and inserting mail into envelopes and applying postage thereto have been generally satisfactory. The limiting area in such automated systems has generally been the stacking and ZIP code-based sorting of mail. Some automated mailing facilities utilize manual labor for the stacking and banding operations, but occupational injuries and increased labor costs have encouraged the use of automated stacking and banding equipment.
One automated prior art mail stacking and separating apparatus has employed a plurality of mail collecting trays or pockets that are mounted on a conveyor chain. Envelopes discharged sequentially from the postage meter mailing machine are discharged into a mail receiving tray or pocket until at least ten pieces and not more than three and one-half inches of mail are stacked in the pocket. The entire conveyor is then moved to position the next tray or pocket for receipt of the next stack of mail.
The problem which has been encountered with this automated mailing system arises from the fact that the envelopes are discharged at a constant, relatively high rate from the postage machine. Thus, the stacking apparatus must move the filled tray from its position for receiving mail and move an empty tray into position to receive mail, all during the interval between sequentially adjacent envelopes.
If an envelope is nine and one-half inches long and is spaced from the next envelope by one inch, the stacking conveyor must be capable of advancing a new tray into position to receive the next piece of mail in less than 0.06 seconds for a postage meter mailing machine operating at 6,000 pieces of mail per hour. Since the entire conveyor belt and all of the trays must be simultaneously moved during this very short interval, a powerful conveyor drive motor is required to overcome the inertia at rest of the conveyor, even though the distance moved is not that great. Rapid and accurate displacement of the conveyor, however, is difficult to achieve, and the cost of such a powerful motor and controls for the same is substantial. Moreover, 6,000 pieces per hour is close to the maximum practical limit possible using such a stacking conveyor.
Not only would it be highly desirable to have a mail stacking apparatus which could accommodate existing high-speed postage machines, there already are labelers which will operate at 35,000 pieces per hour and web press printing machines that operate at 60,000 to 70,000 pieces per hour. Accordingly, there is considerable need to increase the rate at which stacking and sorting of mail or similar printed matter can be accomplished.
Other forms of apparatus for the stacking of sheet material are found in the prior art, but such apparatus has been used for items such as newspapers, shingles, napkins, plaster board and the like, not mail. Typical of such prior art sheet stacking apparatus are the devices shown in U.S. Pat. Nos. 3,205,794; 3,532,230; 3,599,807; 3,861,537; 4,460,169 and 4,562,650.
U.S. Pat. No. 3,205,794 to Califano, et al. is directed to an apparatus for stacking and squaring sheets of shingle material. The stacking apparatus includes a pair of "star wheels" having blades which receive sheets of shingle material from a conveyor belt. Once a stack of six to eight sheets have been received on the star wheels, the wheels are counter-rotated in synchronism to release the stack to drop under the influence of gravity to a stack squaring station. After the stack is squared, it again drops to a conveyor to leave the stacking apparatus.
While the sheets in the Califano, et al. device are advanced into the star wheels at a high rate of speed, namely, 350 feet per minute, sequentially adjacent sheets have to be spaced from each other by a distance which will allow the group or stack of shingles to gravitate or drop out of the way of the star wheels during counter rotation to be in a position to receive the next sheet. This requires a minimum separation between sheets of approximately 5 to 6 inches for shingles having a thickness of 1/8th to 3/16ths of an inch. The interval between sheets of shingles is 0.07 to 0.085 seconds. Such an interval between envelopes in an automated mailing machine system would be equivalent to between about 4,000 to about 5,000 pieces of mail per hour. While constituting a substantial rate, it still falls far short of desired target.
U.S. Pat. No. 3,532,230 to Gutberlet, et al. discloses a high-speed stacker for newspapers in which there are pairs of arms on a vertical conveyor that receive newspapers in sequence from a printer. The blades in the stacker are merely lowered until they interrupt the sequential feeding and start a new stack, with each stack being dropped under the influence of gravity onto a conveyor when the blades reach the bottom of the stacker conveyor. This system does not depend upon re-indexing a stacker in the interval between papers, which, in fact, are overlapped as they are received into the stacker.
Another newspaper stacking apparatus is disclosed in U.S. Pat. No. 3,599,807 to Hedrick. The Hedrick stacker is similar to Gutberlet, et al. in that it uses pairs of blades on a vertical conveyor which are driven to intercept overlapped newspapers so as to divide papers into separate stacks. No attempt is made at indexing during an interval between papers.
Another newspaper stacking machine is shown in U.S. Pat. No. 3,861,537 to Duchinsky, et al. The Duchinsky, et al. stacker forms a bundle of newspapers from a plurality of piles of newspapers. A rotary mechanism is used to lift the piles from beneath the bundle to thereby effect stacking of the piles into the bundle. The apparatus, however, is not designed to effect formation of the piles initially and does not have to solve the timing problems associated with formation of the piles.
U.S. Pat. No. 4,460,169 is directed to the stacking of folded napkins or handkerchiefs. A vertical conveyor is employed with counter-rotating star wheels being employed to lower napkins one at a time on to the blades of the vertical conveyor, which is steadily lowering to accommodate the additional napkins. The spacing between napkins, however, is substantial, and each napkin is transferred from the star wheel to the vertical conveyor with gravity maintaining the napkins in contact with the star wheels as they rotate.
In U.S. Pat. No. 4,562,650, a stacking apparatus for veneer, plaster board, fiber board or the like is disclosed. The apparatus, however, is essentially a drying apparatus in which a vertical conveyor merely holds the boards in spaced relation while they dry. There is no timing problem with respect to the separation of stacks.
Accordingly, it is an object of the present invention to provide an automatic mail stacking and separating apparatus and method which are capable of high-speed separating of mail into ZIP code-based stacks for banding and bulk-rate mailing.
Another object of the present invention is to provide an automatic mail stacking and separating apparatus having greatly increased thruput capacity.
Another object of the present invention is to provide an automatic mail stacking and separating apparatus and method which can be used with and retrofit to a wide range of automatic postage machines.
A further object of the present invention is to provide an automatic mail separating and stacking apparatus which is more reliable and jam-free in its operation.
Still another object of the present invention is to provide an automatic mail separating and stacking apparatus which is easily adjusted to accommodate mail of various sizes.
Another object of the present invention is to provide an automatic mail stacking and separating apparatus which forms and delivers mail to banding apparatus in neat, uniform stacks for ease of banding.
Still a further object of the present invention is to provide an automatic mail stacking and separating device which can be used with computerized mail assembly systems, high-speed labelers and web press printing machines to enable mailing at pre-sort mailing rates.
Another object of the present invention is to provide an automatic mail stacking and separating apparatus and method which is relatively inexpensive to construct and operate, is durable, requires less supervision and reduces operator fatigue.
The automatic mail separating and stacking apparatus and method of the present invention have other objects and features of advantage which will become apparent from and are set forth in more detail in the accompanying drawing and following description of Best Mode Of Carrying Out The Invention.